This invention relates to inkjet printers with automatic sheet feeders which are capable of feeding multiple types of media. More particularly, the invention relates to adjustment mechanisms for optical media sensors for ink jet printers.
Ink jet printers are becoming much more common as the printer of choice because of their relatively lower cost compared to laser printers and the ability of ink jet printers to produce multi-color images on a variety of media types at reasonable costs per printed sheet. Recent improvements in ink jet printers include improvements in the print heads and the ink cartridges and improved or specialized ink formulations. These improvements have led to improved print quality which results in the ability to produce high quality and/or photographic images. As the use of ink jet printers continues to expand, the ability to produce images on a variety of print media has also expanded. For many applications, the type of print media used in an ink jet printer has little effect on the usefulness of the resulting printed product. However, for specialized applications such as the production of photographic quality images and the printing of images on film, high quality paper and the like, it is important to identify to the printer the media being utilized. Absorbent media such as paper requires shorter drying times and can generally accept more ink per droplet than polymeric films or less absorbent print media. Upon identification of the media, adjustments such as print speed, sheet feed rate, ink droplet size, and the like may be changed to be more compatible with the media.
Media sensors have been used for detecting the presence and type of media in a printer. Despite such descriptions, there remains a need for a device or apparatus which can reliably maintain a media sensor in a proper orientation with respect to the print media plane regardless of the media thickness, amount or type used in the printer.
With regard to the foregoing and other objects, the invention provides a media sensor adjustment device for maintaining a media sensor in a preselected orientation with respect to print media prior to feeding the print media to a printing position within the printer. The adjustment device includes frame members, a media sensor housing attached to the frame members for holding a media sensor adjacent to a media surface, and means for maintaining the sensor housing in a substantially fixed orientation relative to a media surface so as to maintain an optical surface of the media sensor substantially perpendicular to an optical path extending from the surface of the sensor to a plane defined by the media surface.
In another aspect, the invention provides an inkjet printer including a printer carriage area containing a carriage, printheads and ink cartridges attached to the carriage and means for moving and activating the printheads for printing on print media. A media support is provided adjacent the printer carriage area for containing a media web, the media web having a media surface defining a media plane. An optical media sensor adjustment device is attached adjacent the media support. The adjustment device includes frame members, a media sensor housing attached to the flame members for holding a media sensor adjacent the media web and for maintaining the sensor housing in a substantially fixed orientation relative to the media surface so as to maintain an optical surface of the media sensor substantially perpendicular to an optical path extending from the surface of the sensor to a plane define by the media surface.
An advantage of the invention is that the sensor adjustment device provides a method and apparatus for reliably maintaining a media sensor in a position relative to a plane defined by the surface of the print media which assures more accurate identification of the media regardless of the media type, thickness or stack height. As described in more detail below, the apparatus of the invention suitably maintains a print media sensor in an orientation which is substantially optically perpendicular to the media surface regardless of the stack height and at a predetermined distance regardless of the media thickness. The terms xe2x80x9csubstantially optically perpendicularxe2x80x9d and xe2x80x9csubstantially parallelxe2x80x9d mean that a plane defined by an operative surface of the sensor is maintained within xc2x1 3.5 degrees of rotation with respect to x and y axes which lie in the plane of the print media.